Choosing a new power supply is not always as easy as one might think. Generally, people just ask how many watts a PSU gives off but that is not enough to make a judgment on which PSU to select. All power supplies are designed differently. Fans, heat sinks, capacitors, etc. are all different in power supplies. The use of quality parts is important.
The first step to choosing a good power supply is finding out how many watts it needs to be after it is determined, what wattage the PSU needs to be then it is time to look for the right one. Different brands of power supplies are made differently, some with larger heat sinks, capacitors, more fans, etc. A general way some test for power supplies is by the actual weight of the unit. Most generic PSU are very light meaning they have small capacitors, less fans, and small heat sinks.
Features and Specifications
The OCZ PowerStream power supply has produced a decent following by providing innovative features. The ModStream is aimed at hardcore modders by incorporating a modular cabling scheme while maintaining the high quality of its sibling. The features table below is taken directly from OCZ…
EZMod Advanced cable management system
EZMod technology allows you to truly customize your power system to utilize on the UV cables you require, resulting in optimal airflow and the coolest possible environment within your case! All EZMod cables glow brightly when illuminated with UV lighting accessories. Powerful 450/520 Watt power supplies with 550/620 Watt Peak Load, designed specifically for the most demanding computing environments of gamers, PC enthusiasts, and power users.
Silent Operation
High performance doesn’t have to come with annoying fan noise, and OCZ PowerWhisper technology effectively reduces noise levels to a minimum, making this the quietest power supply on the market!
Cleaner Power
The OCZ ModStream features PowerShield EMI control technology with copper shielded leads to provide the added benefit of extremem current stabilizationand delivery of the cleanest possible output to all your critical system components.
Run Cooler
Experience leading edge reliability and performance with increased air flow, courtesy of a whisper quiet yet extremely vigourout 120mm fan complete with attractive blue LEDs.
OCZ 3-Year Warranty
The best PSU comes backed with the finest warranty, and OCZ offers an exclusive 3 year PowerSwap warranty program, providing unsurpassed peace of mind. No more endless return-for-repair loops!
OCZ offers an exclusice 3 year PowerSwap warranty programming. If the power supply fails, OCZ will swap it out for a new unit, no questions asked. Here are some additional features of the unit:
- OCZ PowerWisper Technology with 120mm fan
- OCZ PowerShield PCI-Express lead
- OCZ EZMod advanced cable management system
- Supports ATX/BTX/PCI Express/SATA
- 3 Year Warranty backed by OCZ’s exclusive PowerSwap replacement program
- 160 x 150 x 86mm
- 95-132 Vac / 190-264 Vac 10/6a
The power supply itself is wrapped in a custom-made bubble-wrap “box”. Inside the main box is a separate cardboard container with all the cables, a well-written manual, zip ties, bonus Velcro wraps and an unusually beautiful power cord. The power cord features copper mesh around the cables, a circular ferrite bead near the connector, and a translucent blue plastic, which matches perfectly with the look of the power supply. The included power cord is more flexible than a standard black or grey power cable. The included EZmod power cables consist of:
- 1x single 4-pin cable
- 2x dual 4-pin cables
- 1x dual 4-pin cables with floppy connector
- 1x PCI Express 6-pin connector (17”)
- 1x dual SATA connector (25”)
All of the EZmod cables are EMI shielded (with copper braiding to reduce electromagnetic interference) and react to UV lighting. The copper braiding, which is actually silver in color, covers the actual wires, and clear plastic tubing encases the copper braiding. The ends of the tubing are zip-tied and then encased in blue heatshrink is to keep the stuffed cables tidy. All cables are molex based, except for the PCIe and SATA cables which plug into a 6-pin connector. Because the SATA cables are native, they have 5 lines (an extra +3.3V line) instead of the 4 used in SATA power adapters. Although current SATA drives do not use the +3.3V line, SATA2 might. The PCIe cable has a ferrite core encased in the heatshrink to prevent radio interference. The cables are a little stiff, but not unflexible, and the plastic tubing likes to cling when it contacts other tubes. These properties pretty much keep the cables in the position you put them in, and works best when the cables are clustered together, branching off as needed.
A closer look inside
We decided to take a look at the inner workings of the power supply. The cover is fastened to the power supply chasis with four screws (one of which is covered by a voided warranty warning). Once removed we could see the quality and craftsmanship that went into this power supply.
The 120mm fan’s cabling is carefully tucked behind the transformer’s large black-anodized aluminum heatsinks.
There is a small amount of space between the circuit board and case, probably to fit an 80mm fan using another design. The included 120mm fan is crystal clear and has 4x 5mm blue LEDs at each fan corner. There also appears to be extra circuitry modules for line protection. Each molex connector is individually wired (unlike the X-connect which power all ports from one line) which should help stabilize the unit’s rails.
What are “Rails?”:
PC enthusiasts sometimes talk that their “rails” are low and that they need a new power supply. First off, the “rails” that they are referring to are the 3.3V, 5V, and 12V lines that come off the power supply. The 3.3V and 5V generally power the digital devices like the motherboard, PCI slots, AGP slot, etc. The 12V is usually for motorized devices like the hard drives, CD-ROM, fans, etc.
These lines are rated to run at a certain specification, usually somewhere around plus or minus 5%. Technically, if these lines stay within this margin, the system should run fine with no instabilities but if they do run out of specification a number of problems can arise. Usually power supplies go under the minimum voltage when used over a long period of time.
When the rails are low this usually leads to blue screens and various other instabilities like random reboots. When these lines are overvolted problems arise again like drive failure, blue screens, damaged drives and damaged motherboards. Therefore, it is easy to see why it is important to have “clean” power – power that is stable, does not fluctuate, and within a tight tolerance.
High-quality power supplies also help protect your systems. A good power supply will not be damaged during a power outage, brownout, or spike (like 2,500V from a lightning strike). Decent power supplies have an extremely low current leakage to ground of less than 500 microamps. This safety feature is important if your outlet has a missing or an improperly wired ground line. I experienced the ModStream’s power protection first hand when I accidentally arced the wrong wire during testing and shut down the entire system. I thought my entire system was toast, but everything was fine after resetting the power supply. You never realize how important this protection is until you need it.
Many people complain about their power supplies not giving enough voltage to the lines. Many use hardware monitors like the ones available in the BIOS, Motherboard Monitor, Winbond monitor, etc. These are all software based and can be inaccurate. They are approximate reading from the motherboards chips. So just because these software reading say lines are low does not mean it is the power supplies fault. There are many other factors included. Most of the main factors all occur within the motherboard and not the power supply. The voltages given from the power supply have to go through the motherboard before the software reading is taken. Therefore, there are different resistances on the motherboard that the power has to pass through. For instance, the power connectors on the motherboard could be damaged or not making good contact.
Other factors are resistances along the way to the motherboards voltage regulators. Also over time, especially when overclocking, the circuitry will degrade on the motherboard. All of these things can play a roll on how much voltage is lost on the way to the software reading. Therefore, the only true way to test if the power supply is doing its job is to take the voltage readings direct off the power supply and not the motherboard or the software readings. We find this way to be much more precise and accurate. The winbond chips on my motherboards have always been inacurate. For example, software such as Motherboard Monitor reports that my -12V line is running at 8 volts and the -5V line is running at 2.5 volts. A quick check with a multimeter revealed that these rails were perfectly fine.
The OCZ ModStream is ATX12 compliant. Not only does this specification require native SATA, PCIe and ATX12 motherboard connectors, but must also have a 70% efficiency rating, which should help reduce electricity costs. A power supply can never be 100% efficient due to the nature of electronics. A transformer has coil windings to generate an electromagnetic field and then must induce current in another set of windings. A certain amount of power is required to saturate the windings and generate the magnetic field, even though no work is being done.
A power transformer that is not connected to anything is a perfect example of a pure inductive load. An apparent power draw exists to generate the fields, but no working power exists because no actual work is being done. When the transformer is connected to a load, it uses both working power and reactive power. In other words, power is consumed to do work (for example, if the transformer is powering a light bulb), and apparent power is used to maintain the electromagnetic field in the transformer windings.
Normally I don’t list every fan and little piece of equipment in my setup, but every little bit counts when testing a power supply. Each USB device takes up 5 watts of power (especially when the device is powered directly from the bus). The Chenming case offers plenty of airflow, and the list of peripherals is common in many enthusiast’s systems.
| Test system | |
| Chenming Aluminum case | Abit IC-7 motherboard |
| Intel Pentium 4 2.8Ghz 800FSB | 4x 512MB DDR400 RAM (2GB total) |
| MSI GeForce FX 5900 | Soundblaster Audigy sound card |
| LiteOn 8x DVD writer | LiteOn 16x DVD drive |
| 3 PCToys tri-LED 80mm fans | 1 92mm fan |
| Zalman CNPS7000Cu heatsink | Waffer PC Aircon 400 |
| 2x Western Digital 120GB HDD | Microsoft cordless Desktop Elite |
| Wacom USB tablet | Logitech USB Wingman cordless game pad |
| 3 cold cathode lights | Zalman ZM-MFC1 fan controller |
| Hewlett-Packard iPAQ Pocket PC | Creative Labs Nomad Zen Xtra |
The following table lists the wattage requirements of various PC equipment and which rails they use. This is a guide only, but generally faster drives and more advanced processors and video cards will consume more power than ones listed.
| Component | Requirement | Line(s) Used |
| AGP Video Card | 30 – 50W | +3.3V |
| Average PCI Card | 5 – 10W | +5V |
| 10/100 NIC | 4W | +3.3V |
| SCSI Controller PCI Card | 20W | +3.3V and +5V |
| Floppy Drive | 5W | +5V |
| CD-ROM | 10 – 25W | +5V and +12V |
| DVD-ROM | 10 – 25W | +5V and +12V |
| CD-RW | 10 – 25W | +5V and +12V |
| 7200rpm IDE Hard Drive | 5 – 20W | +5V and +12V |
| 10,000rpm SCSI Drive | 10 – 40W | +5V and +12V |
| Case/CPU Fans | 3W each | +12V |
| Motherboard (w/o CPU or RAM) | 25 – 40W | +3.3V and +5V |
| RAM | 10W per 512MB | +3.3V |
| Pentium III Processor | 38W | +5V |
| AMD Athlon Processor | 70W | +12V |
| Pentium 4 2.8Ghz | 89W | +12V |
| GeForce FX 5900 | 85W | +5V and +12V |
| Waffer PC Aircon 400 | 52W | +12V |
| USB | 5W each | +12V |
| Cold cathode light | 10W each | +12V |
Some may not understand how the negative rails are used, or why they are even necessary. Power supplies generally don’t offer much output (usually 1 amp or less) on each of these negative rails, and they are usually consumed only by the motherboard. Negative electricity sounds like an abstract concept, but is really a reference to how it is measured. While positive rails are measured on a sine wave from ground to voltage, negative rails are measured from the voltage to ground, and therefore shown as a negative value.
How we tested
Power readings were taken by back-probing the individual rails with a multimeter using the PC’s aluminum case as ground. Temperatures were taken from the back of the unit using a Radio Shack IR thermometer. I used several quick scans and recorded the highest temperature. System temps were taken from one sample inside the case using the same thermometer. Load was simulated by running 3dMark 2005 with all fans running at full blast. Full load was simulated using the heavy-hitting Waffer Aircon, fans at full blast, copying a DVD movie and running 3DMark 2005. 514 watts estimated use under this configuration, utilizing the PSU at 97%.
| +3.3 | +5 | +12 | -12 | -5 | temp | system | |
| idle | 3.36 | 5.09 | 12.16 | -12.3 | -5.07 | 95 | 88 |
| Load (~70%) | 3.32 | 5.11 | 12.09 | -12.39 | -5.09 | 103 | 88 |
| Extreme load (~97%) | 3.33 | 5.13 | 11.80 | -12.3 | -5.09 | 110 | 89 |
| Loose Tolerance | Tight Tolerance | |||
| Desired Voltage | Min. (-10%) | Max. (+8%) | Min. (-5%) | Max. (+5%) |
| +3.3V | 2.97V | 3.63V | 3.135 | 3.465 |
| +/–5.0V | 4.5V | 5.4V | 4.75 | 5.25 |
| +/–12.0V | 10.8V | 12.9V | 11.4 | 12.6 |
Many power supplies fluctuate after 70% load, but there was none in the OCZ ModStream, even at 97% load, which is a testament of its clean power. The readings on all rails remained stable throughout the test, even during extreme load. Under this heavy load the ModStream only varies by 2%, and only by 1% under normal conditions. Other power supplies that advertise a 1% margin cost over $200. There is a decent amount of air released from the back of the PSU, but generates virtually no noise because of the large amount of space in the back grill. I even put my ear right up to the unit and could hear no noise, as 120mm fans move alot of air while being very quiet.
A 500 watt power supply is not for running at 500 watts all the time… it’s for 400 watts normal usage with peaks of 500 supplying stable power. 520 watts may be overkill for some people, but most users keep their power supplies through several PC upgrade life cycles and should consider their PSU a long term investment. Unfortunately the unit is not perfect, but a few features would definately push it over the top. Since the unit boats a modular design, it would be nice to see the motherboard connectors as seperate cables, as not everyone has an ATX12 motherboard right now. Also, many modders would like to see a UV reactive window in different colors (like the X-connect). One last wish would be to include the adjustable rails and dual +12V rails present in OCZ’s popular PowerStream units. These additional features would definately land this unit a perfect score, as the quality is top notch.
| Quality | 10 |
| Design/Looks | 9 |
| Value | 9 |
| Features | 8 |
| Performance | 10 |
| Innovation | 9 |
| Noise | 9 |
| Average | 9 |
It is far less trouble to buy a quality power supply from the start than to troubleshoot system instability. The OCZ modstream delivers quality performance similar to much more expensive units (like PC Power & Cooling) for much less, and has the modular features that keep your system tidy. The unit is future ready and has killer looks. Summing up all the aspects of this product yield a 9 out of 10 rating and the OCmodshop seal of approval.
Pros
- Stable power with strong voltages and little fluctuation
- Looks good
- EMI shielding
- Virtually noiseless
- Flexible connectivity
- ATX12 compliant (native SATA, PCIe, and ATX12 motherboard connectors)
- Excellent build quality
- Modular design (use only what cables you need)
- One of the best warranties in the business
Cons
- No adjustable voltage regulation
- Motherboard connectors not completely modular